Pseudomonas fluorescens and low doses of chemicals inhibit postharvest decay of apples in commercial storage

Figures & data

Fig. 1 Inhibitory effect of P. fluorescens isolates 1–112, 2–28 and 4–6 on mycelial growth of B. cinerea on ¼ TSA-PDA amended with no chemicals (NC) or amended with calcium chloride (CaCl₂), sodium bicarbonate (SBC) or salicylic acid (SA) after 72 h incubation at 25°C. Data represent the mean ± standard error from two independent experiments. Means followed by a common letter are not significantly different according to Tukey’s test (P < 0.05).

Control,

1–112,

2–28,

4–6.

Fig. 2 Inhibitory effect of P. fluorescens isolates 1–112, 2–28 and 4–6 on mycelial growth of M. piriformis on ¼ TSA-PDA amended with no chemicals (NC) or amended with calcium chloride (CaCl₂), sodium bicarbonate (SBC) or salicylic acid (SA) after 72 h incubation at 25°C. Data represent the mean of three replicates ± standard error. Means followed by a common letter are not significantly different according to Tukey’s test (P < 0.05).

Control,

1–112,

2–28,

4–6.

Fig. 3 Inhibitory effect of P. fluorescens isolates 1–112, 2–28 and 4–6 on mycelial growth of P. expansum on ¼ TSA-PDA amended with no chemicals (NC) or amended with calcium chloride (CaCl₂), sodium bicarbonate (SBC) or salicylic acid (SA) after 72 h incubation at 25°C. Data represent the mean of three replicates ± standard error. Means followed by a common letter are not significantly different according to Tukey’s test (P < 0.05).

1–112,

2–28,

4–6.

Fig. 4 Grey mould (a) lesion diameter and (b) disease incidence of ‘Ambrosia’ apples after 15 weeks in commercial controlled atmosphere storage at 0°C. Apples treated with B. cinerea were also subjected to treatment with each isolate of P. fluorescens, 1–112, 2–28 or 4–6, or BioSave® or Scholar®. Control apples were treated with the pathogen only. Each bar represents the mean of three replicates of 10 apples each ± standard error. Different letters indicate significant differences according to Tukey’s test (P < 0.05).

Fig. 5 Mucor rot (a) lesion diameter and (b) disease incidence of ‘Ambrosia’ apples after 15 weeks in commercial controlled atmosphere storage at 0°C. Apples treated with M. piriformis were also subjected to treatment with each isolate of P. fluorescens, 1–112, 2–28 or 4–6, or BioSave® or Scholar®. Control apples were treated with the pathogen only. Each bar represents the mean of three replicates of 10 apples each ± standard error. Different letters indicate significant differences according to Tukey’s test (P < 0.05).

Fig. 6 Blue mould (a) lesion diameter and (b) disease incidence of ‘Ambrosia’ apples after 10 weeks in commercial controlled atmosphere storage at 0°C. Apples treated with P. expansum were also subjected to treatment with each isolate of P. fluorescens, 1–112, 2–28 or 4–6, or BioSave® or Scholar®. Control apples were treated with the pathogen only. Each bar represents the mean of three replicates of 10 apples each ± standard error. Different letters indicate significant differences according to Tukey’s test (P < 0.05).

Table 1. Effect of P. fluorescens isolate 4–6 alone or in combination with calcium chloride (CaCl₂), sodium bicarbonate (SBC) or salicylic acid (SA) in comparison to the registered biological control agent, BioSave® and fungicide, Scholar® on the lesion diameter of B. cinerea, M. piriformis and P. expansum on ‘Ambrosia‘ apples.

	Lesion diameter (mm) after 15 weeks in cold storage at 0°C
Treatment	B. cinerea	M. piriformis	P. expansum
Control	42.7^1 a^2	78.9 ab	27.4 a
4–6	1.1 b	80.9 a	11.6 bcd
4–6 + CaCl2	0.5 b	72.2 abc	10.5 bcd
4–6 + SBC	0.0 b	44.3 d	4.2 de
4–6 + SA	2.2 b	80.3 a	8.0 cd
CaCl2	2.2 b	50.1 cd	4.8 cde
SBC	0.0 b	52.1 cd	13.9 abc
SA	5.5 b	86.0 a	22.1 ab
BioSave®	37.6 a	57.6 bcd	8.3 cd
Scholar®	0.3 b	38.3 d	0.2 e

¹ Each value represents the mean of three replicates of 10 apples each.

² Different letters within a column indicate significant differences according to Tukey’s test (P < 0.05).

Table 2. Effect of P. fluorescens isolate 4–6 alone or in combination with calcium chloride (CaCl₂), sodium bicarbonate (SBC) or salicylic acid (SA) in comparison to the registered biological control agent, BioSave® and fungicide, Scholar® on the disease incidence of B. cinerea, M. piriformis and P. expansum on ‘Ambrosia‘ apples.

	Disease incidence after 15 weeks in cold storage at 0°C
Treatment	B. cinerea	M. piriformis	P. expansum
Control	70.0^1 a^2	86.7 abc	65.0 a
4–6	1.7 b	86.7 abc	33.3 bc
4–6 + CaCl2	3.3 b	81.7 bcd	31.7 bc
4–6 + SBC	0.0 b	51.7 e	15.0 cd
4–6 + SA	3.3 b	88.3 abc	31.7 bc
CaCl2	3.3 b	63.3 cde	16.7 c
SBC	0.0 b	60.0 de	41.7 abc
SA	10.0 b	96.7 ab	53.3 ab
BioSave®	76.7 a	96.7 a	66.7 a
Scholar®	5.0 b	41.7 e	1.7 d

¹ Each value represents the mean of three replicates of 10 apples each.

² Different letters within a column indicate significant differences according to Tukey’s test (P < 0.05).